Autodesk/revit-ifc

INQ: Subcategory Mapping

Opened this issue · 3 comments

Inquiry description

What is the purpose of subcategory level mapping of ifc classes in the IFC Export Classes Mapping?It seems to have no effect, not even when building parts are exported, so I assume nothing, and it is only a leftover of the outdated cad layer mapping dialog and config file. This is totally confusing.
Do they have any sideeffects?

Revit Version

2024.0.x

IFC for Revit Addon Version

24.x.x

Windows Version

11 22H2

It is used in certain cases where an element has a sub-category assigned to it at the highest level. For example, there are different types of massing (mass floor, e.g.) and they are controlled by the sub-category. I think lines also have sub-categories. There may be a few more. For parts, do they have a sub-category? If so, then that could just be a missed case that we could add support for.

Okay, for massing it makes sense, but I don't really consider them actual building elements that have their roles in an Ifc model, but whatever. Same goes for lines, honestly. I think this confusion also asks for better UI/UX of default category mapping, just like in #747

Regarding parts, yes and no. For composite structures the parts are created from specific layers, that have their own subcategory from their function, but AFAIK the generated parts won't know their "subcategory" anymore, not directly, at least. The only thing they know is whether they are part of the core or not. I haven't checked if this info is available through the API.

Just to be clear, is this related to the Revit 2025 changes or before them?